1. Field of the Invention
The present invention relates to the field of design and construction of two wheeled vehicle frames such as bicycle and motorcycle frames. More particularly, the present invention relates to the field of design and construction of the inner tube for front suspension forks for two wheeled vehicles such as bicycles and motorcycles.
2. Description of the Prior Art
A front fork for a two wheeled vehicle such as a motorcycle or bicycle typically includes the following main components: a steering tube, a crown, and two front legs. The steering tube is connected to the handlebar. The crown interconnects the steering tube and the two front legs.
Many bicycle or motorcycle fork legs now utilize various suspension systems. Commonly a suspension leg utilizes a telescoping assembly which includes an upper tube and a lower tube. The upper and lower tubes are slidably engaged with damping devices to form a suspension leg. The crown is connected to the top ends of the upper tubes.
One problem encountered in design and construction of the telescoping assembly is the strength of the tubes. The tubes are constantly subject to the weight, torsional and side loading forces from the handlebar (through the steering tube and the crown) and the front wheel axle. This is a particular concern for the inner tubes which is necessarily thinner than the outer tubes in the telescoping assembly.
For example, in a telescoping assembly where the upper tube is slidably inserted into the lower tube, the upper tube is the inner tube and the lower tube is the outer tube of the telescoping assembly. The lower part of the inner tube is inserted and travels within the outer tube, but the upper part of the inner tube stays outside of the outer tube and is exposed. Therefore, while the lower part of the inner tube is braced and bolstered by the outer tube, the upper part of the inner tube is not supported by the outer tube. Moreover, since the top end of the inner tube is connected to the crown, it further bears the stress from the handlebar.
Therefore, it is desirable to provide reinforcement to the legs of a bicycle or motorcycle forks. Particularly, it is desirable to provide reinforcement at the top ends of the legs where the crown is connected. More particularly, it is desirable to reinforce the exposed part of the inner tubes of the telescoping assemblies at the location where the inner tube is attached to the crown.